<!DOCTYPE html>
<html>

	<head>
		<meta charset="UTF-8">
		<title></title>
	</head>

	<body>
		<style>
			button {
				font-size: 18px;
				font-family: '华文行楷';
			}
		</style>
		<button>我是一个普通的按钮</button>
		<div></div>

		<script>
			var host = document.querySelector('div');
			var root = host.createShadowRoot();
			root.innerHTML = '<style>button { font-size: 24px; color: blue; } </style>' +
				'<button>我是一个影子按钮</button>'
		</script>
	</body>

</html>